Type 2 diabetes (T2DM) develops in 50% of women with gestational diabetes (GDM) within 5 years after delivery. So far, no lifestyle interventions have been translated for women with GDM in the postpartum period. Screening for GDM as currently practiced allows for efficient identification of a population at high risk of T2DM. The main goal of this study is to examine the comparative effectiveness of diabetes prevention strategies in women with gestational diabetes (GDM) for improving the following: obesity, hyperglycemia, hypertension and depression in a real-world clinical setting. It is a cluster randomized lifestyle intervention trial that assesses the effect of an organizational-level intervention on weight management in GDM patients. Randomization will occur at the medical center level;44 medical centers of Kaiser Permanente Northern California (KP) will participate and data will be collected for more than 2,400 pregnant women with GDM (36% Asian, 31% Hispanic, 25% white, 4% African American and 5% other ethnic groups). The intervention will be compared to usual care. The intervention will extend an existing KP case-management program offered by the KP Perinatal Center to patients with GDM during pregnancy. Intervention patients will be offered a postpartum lifestyle curriculum of individual telephone counseling augmented with e-mails and an interactive study website. The intervention will be delivered by dieticians trained in social cognitive strategies and motivational interviewing techniques. The primary aim is to implement and evaluate an intervention of diet and physical activity (PA) with the primary goals of: a) reaching pre-pregnancy weight for women with a normal weight prior to pregnancy;or b) reaching a 5% reduction of their pre-pregnancy body weight if the women were overweight or obese prior to pregnancy. Targets for the intervention during pregnancy (Prenatal Phase I) are to help GDM patients comply with IOM guidelines for gestational weight gain. The Early Post-partum Phase II intervention begins at 6-weeks postpartum and will be delivered through 12 telephone counseling calls over a period of 4 months, after which the maintenance phase (Late Post-partum Phase III) will begin. The primary study outcomes will be the proportion of women who reach their postpartum weight goal and the total amount of weight change. Secondary outcomes will include postpartum glucose levels, blood pressure, depression, dietary fat intake, total calories and PA. Measurements will be taken during pregnancy at study entry and at 6-weeks, 6-months and 12-months postpartum. Demographic and psychosocial factors that may be related to success of the intervention will be examined;cost-effectiveness analyses and process measure evaluations are also proposed. This study has been developed in close collaboration with KP clinical operations leaders, who are committed to this intervention. KP clinical operations leaders are eager to assist in the evaluation of this intervention and assess its potential for implementation. Finding that this intervention is cost-effective in this setting should motivate its adoption at KP, as well as in other health care systems. PUBLIC HEALTH RELEVANCE: Type 2 diabetes (T2DM) develops in 50 percent of women with gestational diabetes (GDM) within 5 years after delivery. So far, no lifestyle interventions have been translated for women with GDM in the postpartum period. The main goal of this study is to examine the effect of diabetes prevention strategies in women with gestational diabetes (GDM) for improving the following: obesity, hyperglycemia, hypertension and depression in a real-world clinical setting. It is a cluster randomized lifestyle intervention trial that assesses the effect of an organizational-level intervention on weight management in GDM patients. Randomization will occur at the medical center level;44 medical centers of Kaiser Permanente Northern California (KP) will participate and data will be collected for more than 2,400 pregnant women with GDM (36% Asian, 31% Hispanic, 25% white, 4% African American and 5% other ethnic groups). The intervention will be compared to usual care. The intervention will extend an existing KP case-management program offered by the KP Perinatal Center to patients with GDM during pregnancy. Intervention patients will be offered a postpartum lifestyle curriculum of individual telephone counseling augmented with e-mails and an interactive study website. The primary aim is to implement and evaluate an intervention of diet and physical activity (PA) with the primary goals of: (a) reaching pre-pregnancy weight for women with a normal weight prior to pregnancy;or (b) reaching a 5 percent reduction of their pre-pregnancy body weight if the women were overweight or obese prior to pregnancy. Targets for the intervention during pregnancy (Prenatal Phase I) are to help GDM patients comply with IOM guidelines for gestational weight gain. Finding that this intervention is cost-effective in this setting should motivate its adoption at KP as well as in other health care systems.